1. Field of the Invention
Apparatuses consistent with the present invention relate, in general, to blowing devices and air conditioning apparatuses having the blowing devices and, more particularly, to a blowing device having an air suction guide with an improved structure to reduce operational noise of the blowing device, and to an air conditioning apparatus having the blowing device.
2. Description of the Related Art
Generally, air conditioning ducts and air conditioning apparatuses are typically provided with blowing devices which are disclosed in, for example, Japanese Patent Laid-open Publication Nos. 2000-39199 and 2003-3997. The above-mentioned conventional blowing devices for air conditioning ducts or air conditioning apparatuses include a centrifugal-type blowing fan having a plurality of blades, a motor to drive the blowing fan, and a fan casing which covers the blowing fan and guides inlet air to the blowing fan. The fan casing of the conventional blowing devices has a suction port to draw the air into the fan casing, and an exhaust port to discharge the air from the fan casing to an outside of the fan casing. The fan casing further includes an air suction guide which is provided in the suction port of the fan casing to guide the inlet air to the blowing fan. In the related art, the air suction guide provided in the fan casing is a so-called “bell mouth”.
In the conventional blowing devices, the suction port of the fan casing has a variable inner diameter which is gradually reduced in a direction from an inlet end of the suction port toward the blowing fan, thus providing the air suction guide having a smoothly rounded surface to guide evenly the inlet air to the blowing fan.
However, the conventional blowing device having the above-mentioned air suction guide is problematic as follows. During an operation of the conventional blowing device, the inlet air flows through a peripheral area of the suction port, which is adjacent to the air suction guide, at a speed which is higher than a flowing speed of the inlet air flowing through a central area of the suction port while the inlet air flows to the blowing fan through the suction port due to a suction force generated by the blowing fan. Therefore, a flow rate of the inlet air flowing through the peripheral area of the suction port is higher than a flow rate of the inlet air flowing through the central area of the suction port, so that the conventional blowing device increases an amount of inlet air flowing into the fan casing. However, there is a remarkable variation in a pressure applied onto the blades of the blowing fan by the inlet air, thus the conventional blowing device generates operational noise which upsets those around the blowing device.